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Fuel Burned After a Drag Race

crimson_crowd_eater

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Does anyone know what mpg is returned from drag racing on 93 or how much fuel is burned during a 1/4 mile pass? Just a general question for some physics calculations I'm processing.
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crimson_crowd_eater

crimson_crowd_eater

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who cares per gallon
I mean I guess that's well and good but that doesn't help at all. I was actually trying to use the Mustang as an example of some important physics principles.
 

Shifting_Gears

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Does anyone know what mpg is returned from drag racing on 93 or how much fuel is burned during a 1/4 mile pass? Just a general question for some physics calculations I'm processing.
Iā€™m not a math genius so Iā€™m not going to attempt the calculations, but if you took an injectors flow rating (which is typically rated at lbs per hr) and divide that across the ET of the 1/4mi pass, multiplied by the amount of cylinders you would probably come close. It would give you the weight of the fuel consumed over a pass. From there you could calculate what that equates to in MPG.
 

Zathras

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An extremely crude estimate: gasoline engines typically have a BSFC of about 0.50 lbs fuel per HP per hour. So for a 460 HP engine x 0.5 lb, that's roughly 230 lb fuel/hour. But since a 1/4 mile run only uses full throttle for 12-13 seconds (give or take for a stock S550), that's only 0.0036 hours. 230 x .0036 = 0.83 pounds. Gasoline is about 6 pounds a gallon, so that works out to about 0.14 gallons during the 1/4 mile run. (Ignoring the fuel being used while idling, or during deceleration, etc..)

Not very much, eh?

Oh wait you wanted MPG during the run? well, you went 0.25 miles and used 0.14 gallons, so thats...about 1.8 miles/gallon.
 

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ugstang17

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Iā€™m not a math genius so Iā€™m not going to attempt the calculations, but if you took an injectors flow rating (which is typically rated at lbs per hr) and divide that across the ET of the 1/4mi pass, multiplied by the amount of cylinders you would probably come close. It would give you the weight of the fuel consumed over a pass. From there you could calculate what that equates to in MPG.
Good idea but Fuel injectors don't run at their static ratings (100% PWM) and most setups at WOT don't use all of the injector. Most tuners will only run a fuel injector up to 80-90% PWM. You could guess at 80% PWM which would be 80% of the flow rate, but that would be a guess. Don't think Ford provides a PID to datalog for FI PWM% butthey do datalog fuel pump duty cycle.

You could datalog the dutycycle of the FUEL PUMP throughout the 1320ft hit and figure the amount of fuel delivery based on the fuel pumps flow rate per hour. So say you had a 400LPH fuel pump and it is producing an avg of 60% Duty cycle (which would be 60% of its rated output per hour over an 11 second run the you have your fuel consumption for that run without knowing what the PWM of the fuel injectors are operating at (times 8) and their flow rates which the last time I checked was not PID that Ford datalogs...unless they do on the newer 18+ ECU.

CLASSROOM EXAMPLE -

So a pump that puts out 250LPH (liters per hour) is operating at 60% D.C. at WOT during your pass. This equals a flow rate of 150LPH. The run is 11 seconds at 60% DC. An 11 second run / 3600 seconds in an hour equals 0.00305% of an hour. 150LPH x 0.00305 = 0.458L There are 3.8Liters in one gallon so 0.458L = 0.121 gallons burned to make an eleven second pass or 15.5 ounces. Don't forget to multiply by the number of fuel pumps if you are running multiple pumps.

Of course air conditions will determine how effeciently the fuel generated power but this calculationwill/should get you what you are looking for. All you need to know is the flow rate on your fuel pump(s) and the ET.

This is assuming a returnless system. If return style all bets are off.
 
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ihasnostang

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if you have an obd tool you could use it to check fuel level to nearest 1/10th, and just wait until it rolls over to a new tenth, or start a datalog before the run and you should be able to read gallons per hr and you could export those values at several times a second to an excel file and take the (average?log?) of the run.
 

K4fxd

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You can log Pulse width and duty cycle

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